Peru has declared a state of emergency in the area around the volcano, with further moderate explosions expected. Nearly 30,000 people have been evacuated.
According to Peru's National Emergency Operations Center (COEN), ash from the Ubinas volcano has covered 617 schools and 20 health centers in the southern region of the Andean nation.
The volcano set off a series of explosions last Thursday and emitted a column of ash about 5 kilometers (3 miles) high, which has since drifted with the wind, taking with it toxic gases.
The Geophysical Institute of Peru (IGP) issued an ongoing "orange warning" on Sunday, indicating further moderate explosions and ash emissions were possible.
The majority of those affected by the eruption — 19,000 of the 29,700 — live in the area bordering Bolivia to the east. About 9,000 people to the south, around the town of Moquegua, have also been affected since the volcano erupted last week.
State of emergency
A state of emergency was declared by President Martin Vizcarra after he visited the area. The aim is to accelerate distribution of aid, and speed up evacuations of communities.
Speaking on TVPeru, Jersy Marino of the Mining and Metallurgical Geological Institute (INGEMMET) said there are eight volcanoes in the south of Peru and that Ubinas is "very active," with "eruptions every five or six years."
Peru is located within the 40,000-kilometer, horseshoe-shaped Ring of Fire around the Pacific Ocean, which has 452 volcanoes and a nearly continuous series of oceanic trenches.
Ubinas is the latest in a series of volcanic eruptions which have included Mount Etna on the east coast of Sicily, Popocatepetl in central Mexico and Stromboli, in the Tyrrhenian Sea, off the north coast of Sicily.
About 81% of the world's largest earthquakes occur along the Ring of Fire, according to the US scientific agency, the United States Geological Survey (USGS).